First synthetic entry to the trimer stage of 5,6-dihydroxyindole polymerization: ortho-alkynylaniline-based access to the missing 2,7′:2′,7-triindole

5,6-Dihydroxyindole oligomers are valuable synthetic targets for the structural characterization of eumelanin biopolymers as well as for the realization of bioinspired functional materials. An ortho-alkynylaniline-based strategy allowed the first access to a trimer, the missing 5,5',5,6,6',6-hexaacetoxy-2,7':2',7-triindole, and its detection as a minor intermediate en route from 5,6-dihydroxyindole to eumelanin-like polymers.